Aug 2 (Reuters) - Cigna Corp said on Thursday it was confident of winning shareholder approval for its $52 billion Express Scripts buyout, a day after reports that investor Carl Icahn had picked up a stake in the insurer and was planning to vote against the deal.

"We strongly believe that the combination (with Express Scripts) is in the best interest of our shareholders," Cigna Chief Executive Officer David Cordani reiterated.

The Cigna-Express Scripts deal has drawn investor skepticism over concerns that the ever-growing presence of Amazon.com in the healthcare sector and President Donald Trump's push to cut rebates pharmacy benefit managers receive from drugmakers.

Icahn believes Cigna is paying too high a price for Express Scripts and a combined company will have to face competition from Amazon growing presence in the health-care industry, the Wall Street Journal reported on Wednesday, citing sources.

Cordani said shareholders would vote in the company's favor, based on the strategic rationale of the transaction and ongoing conversation the insurer has had with its shareholders.

The vote is due on Aug. 24. Cigna did not immediately respond to Reuters request for comments on Icahn's stake, which reports said was less than 5 percent.

Analysts, however, do not expect Cigna shareholders to vote down the deal.

J.P.Morgan analyst Gary Taylor said few shareholders have questioned the strategic rationale of the deal as the competitive environment for health insurers if drugstore chain CVS Health's acquisition of health insurer Aetna is approved.

Taylor also noted that there was a significant overlap in shareholding, with Cigna shareholders through various funds also owning nearly 84 percent of Express Scripts.

The company said net income came in at $806 million, or $3.29 per share, in the second quarter ended June 30, compared to $813 million, or $3.15 per share, a year earlier.

Excluding items, Cigna earned $3.89 per share, well above the average analysts' estimate of $3.33, according to Thomson Reuters I/B/E/S.